What is a stepper motor?
The stator winding produces a vector magnetic field as current flows through the stator windings. The magnetic field causes the rotor to rotate an angle such that the pair of magnetic fields in the rotor coincide with the direction of the magnetic field of the stator. When the stator's vector magnetic field is rotated by an angle. The rotor also turns an angle with the magnetic field. Each time an electrical pulse is input, the motor rotates an angle further. The angular displacement of the output is proportional to the number of pulses input, and the rotational speed is proportional to the pulse frequency. Changing the order in which the windings are energized, the motor will reverse. Therefore, the number of control pulses, the frequency, and the energization sequence of the windings of each phase of the motor can be used to control the rotation of the stepping motor.
The various types of motors commonly seen have iron cores and winding coils inside. The winding has resistance, and the power will generate loss. The loss is proportional to the square of the resistance and current. This is the copper loss we often say. If the current is not a standard DC or sine wave, harmonic loss will occur. The core has hysteresis. The eddy current effect also causes loss in the alternating magnetic field, and its magnitude is related to material, current, frequency, and voltage. This is called iron loss.
Both copper loss and iron loss are manifested in the form of heat, which affects the efficiency of the motor. Stepper motors generally pursue positioning accuracy and torque output, the efficiency is relatively low, the current is generally large, and the harmonic components are high, and the frequency of the alternating current also varies with the rotational speed. Therefore, the stepping motor generally has a fever condition, and the situation is more general. The AC motor is serious.
The stepping motor cannot be directly connected to the power frequency AC or DC power supply, but a dedicated stepping motor driver must be used. As shown in Fig. 2, it is composed of a pulse generation control unit, a power driving unit, a protection unit and the like. The two cells enclosed by the dotted line in the figure can be realized by microcomputer control. The drive unit is directly coupled to the stepper motor and can also be understood as the power interface of the stepper motor microcomputer controller.
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